With the increasing down-scaling of integrated circuits and increasingly demanding requirements for a higher speed of integrated circuits, transistors need to have higher drive currents with increasingly smaller dimensions. Fin field-effect transistors (FinFETs) were thus developed. FinFETs have increased channel widths because the channels include sidewall portions in addition to the portions on the top surfaces of the fins. Since the drive currents of transistors are proportional to the channel widths, the drive currents of FinFETs are increased over that of planar transistors.